A spring drive of this type is disclosed in EP-A-0,294,561. A large wheel is seated in a rotationally fixed manner on a rotatably mounted switch-on shaft, on which large wheel a lug is articulated eccentrically with respect to the rotation axis of the switch-on shaft, which lug is connected at the other end to a lever which, for its part, interacts with a switch-on spring which is constructed as a torsion bar. In order to stress the switch-on spring, the large wheel engages with a small wheel which is driven by a drive device in order to drive the switch-on shaft from an original position, in which the switch-on spring is at least partially relieved of stress, via a deadpoint position, in which the line in which the lug acts passes through the rotation axis and in which the switch-on spring is stressed, in the rotational direction. A latching device supports the switch-on shaft in a supported position against the effect of the stressed switch-on spring, which supported position is offset through a small angle in the rotation direction with respect to the deadpoint position. The toothed rim of the large wheel has a tooth gap at that point which is arranged close to the small wheel in the case of a switch-on shaft which is supported on the latching device. This is to prevent the large wheel being driven even further by the small wheel when the switch-on spring is stressed and thus additionally loading the latching device. In order to switch the switch on, the latching device releases the switch-on shaft, which is driven in the rotation direction under the force of the switch-on spring. At the same time, the toothed rim of the large wheel engages with the small wheel again. In order to prevent the first tooth of the large wheel which follows the gap in the rotation direction of the switch-on shaft resting on the tangential apex surface of a tooth of the small wheel and thus preventing the wheel pair from further rotation, and the spring drive in consequence being blocked, the said first tooth is constructed such that it can be forced back in a sprung manner in the radial direction. If, at switching-on, this tooth abuts against the apex of a tooth on the small wheel, it can give way backwards in the direction of the center of the large wheel and thus slide away over the apex surface of the relevant tooth of the small wheel. It then engages in the gap after this tooth on the small wheel and thus synchronizes the small wheel with the large wheel. In the case of this known spring drive, there is a risk that the tooth which is arranged such that it can give way in a sprung manner drives the small wheel as a result of friction. The second, unsprung tooth, following the gap, of the large wheel can then abut against the apex surface of a further tooth of the small wheel and thus block the drive. This risk occurs especially when the small wheel is decoupled from the drive device by means of a free wheel and can therefore easily be rotated. Furthermore, production of the large wheel with a sprung tooth is costly.